Impacts of severe residential wood burning on atmospheric processing, water-soluble organic aerosol and light absorption, in an inland city of Southeastern Europe.

This study examines the concentrations and characteristics of carbonaceous aerosols (including saccharides) and inorganic species measured by PM 2.5 filter sampling and a multi-wavelength Aethalometer during two campaigns in a mountainous, medium-sized, Greek city (Ioannina). The first campaign was conducted in summer and used as a baseline of low concentrations, while the second took place in winter under intensive residential wood burning (RWB) emissions. Very high winter-mean OC concentrations (26.0 μg m−3) were observed, associated with an OC/EC ratio of 9.9, and mean BC wb and PM 2.5 levels of 4.5 μg m−3 and 57.5 μg m−3, respectively. Simultaneously, record-high levoglucosan (Lev) concentrations (mean: 6.0 μg m−3; max: 15.9 μg m−3) were measured, revealing a severely biomass burning (BB)-laden environment. The water-soluble OC component (WSOC) accounted for 56 ± 9% of OC in winter, exhibiting high correlations (R2 = 0.93–0.97) with BB tracers (nss-K+, BC wb , Lev), nitrate and light absorption, potentially indicating the formation of water-soluble brown carbon (BrC) from fast oxidation processes. The examination of diagnostic ratios involving BB tracers indicated the prevalence of hardwood burning, while the mean Lev/OC ratio (22%) was remarkably higher than literature values. Applying a mono-tracer method based on levoglucosan, we estimated very high BB contributions to OC (∼92%), EC (∼64%) and WSOC (∼87%) during winter. On the contrary, low levels were registered during summer for all carbonaceous components, with winter/summer ratios of 4–5 for PM 2.5 and BC, 10 for OC, 30 for BC wb and ∼1100 for levoglucosan. The absence of local BB sources in summer, combined with the photochemical processing and aging of regional organic aerosols, resulted in higher WSOC/OC fractions (64 ± 13%). The results indicate highly soluble fine carbonaceous aerosol fraction year-round, which when considered alongside the extreme concentration levels in winter can have important implications for short- and long-term health effects. [Display omitted] • PM 2.5 chemical characterization in a semi-mountainous city of Southeast Europe. • Severe PM 2.5 , OC and levoglusocan levels are found due to wood burning in winter. • Biomass burning contributes 92%, 87%, 64% to OC, WSOC, EC, respectively in winter. • High levoglucosan-to-OC ratio (22%) is found for local hardwood burning emissions. • Fresh wood burning aerosols were highly water-soluble with implication for toxicity. [ABSTRACT FROM AUTHOR]